tonopah, nv: 1901 to late 1920s+, 1.9 moz au, 174 moz ag ... · formation of high- and...

Formation of high- and low-sulfidation deposits SEG Nevada: May 2013

J.W. Hedenquist 1

Tonopah, NV: 1901 to late 1920s+, 1.9 Moz Au, 174 Moz Ag

Ag-Au intermediate-sulfidation vein

Environments and variations of epithermal gold deposits


J.W. Hedenquist 2


J.W. Hedenquist 3

Broadlands, New Zealand: Pilot plant at well head

K.L. Brown, 1986

FeS2, CuFeS2, + 5 wt.% gold


J.W. Hedenquist 4

Simmons and Browne, 2000

Ohaaki Pool

LS, shallow (<300-400 m) <220-230 C

IS, deeper (~300-800 m) >220-230 C)

musc

Hedenquist et al., 1996


J.W. Hedenquist 5

HS IS LS LS(a)

Ya

RMt

Hedenquist et al., 1996, 2000

Vi To

Wa

Sl


J.W. Hedenquist 6

25 m

Silica sinter

Sheeted gold- quartz vein below sinter

Sherlock et al., 1995

H2S + 2O2 = H2SO4 Steam-heated


J.W. Hedenquist 7

migration of volcanism

Hishikari, southern Kyushu

1 Ma now

Footprint of 11 Moz Au deposit

0.7 Ma


J.W. Hedenquist 8

Hishikari: Gold-quartz veins in greywacke basement

500 m

Hishikari, S Kyushu

Izawa et al. (1990)

tridymite gone

smectite, kaolinite

smectite- chl

highest

paleotemp

Zoned clays around vein projections: high T paleo-plume


J.W. Hedenquist 9

Outflow down valley to distant hot springs

NW SE Old surface, before erosion

smectite-chl

chlorite

smectite, kaolinite


J.W. Hedenquist 10

Sleeper vein

Wood vein

West Wood

vein Opt 0.05 - 0.10 0.10 - 0.25 0.25 -0.50 0.50 - 1.0 >1.0

Sleeper mine blast hole Au contours

Courtesy of X-Cal

~500 m


J.W. Hedenquist 11

Sleeper pit Long section 16

(blast hole data, 50’)

Courtesy of X-Cal

200 m

Courtesy of Jim Saunders

1 cm

Opt 0.05 - 0.10 0.10 - 0.25 0.25 -0.50 0.50 - 1.0 >1.0


J.W. Hedenquist 12

Saunder and Einaudi, 1990

1 9

2 4, 8


J.W. Hedenquist 13


Quartz-adularia-sericite

Argillic

SilicificationA BAlteration

A

B

FairviewHill

N

1600

1800

2000(m)

500 m

StebbinsHill

Round Mtn.

Argillic

Chlorite



J.W. Hedenquist 14

Sillitoe and Hedenquist, 2003

Lake beds

Sillitoe, 2010 Economic Geology

Porphyry systems: arcs

Base of lithocap

Porphyry Cu-Au

High-sulfidation Au-Cu

Intermediate sulfidation

Au-Ag (Pb-Zn)

Proximal Cu-Au skarn

Distal Pb-Zn skarn

Replacement Zn-Pb-Ag


J.W. Hedenquist 15

≤800oC hypogene vapors, HCl, SO2

High-temperature hypogene vapors, ≤850 oC with HCl, SO2


J.W. Hedenquist 16

Porphyry systems Sillitoe, 2010

Base of lithocap Early: High T magmatic   Coupled brine + vapor   Potassic (~500oC) +

advanced argillic lithocap   Wavy qtz veins, no halo   Metal sulfides

pH 1-2, H2SO4

HCl

Quartz-alunite, barren

Residual quartz (vuggy), barren

acidic stream, pH ~0.6

pH~0.2

White Island, New Zealand: drowned fumaroles, 2007

Satsuma Iwojima, Japan Fluid:rock reaction


J.W. Hedenquist 17

Sampling of 770 C vapor with acidic gases

dissolved rock


Satsuma Iwojima, Japan

pH 1.7 -- 1.1


J.W. Hedenquist 18

Steven and Ratté, 1960

Summitville, Colorado

Steven & Ratté, 1960

pH ~ >6 4 - 6 2 - 4 <2

10 - 100s m


J.W. Hedenquist 19

>10 g/t 500 m

Residual quartz, vuggy: Summitville Quartz-alunite, Summitville

Hypogene alunite, El Tambo Residual quartz, vuggy: Pierina

Arribas et al., 2000

Residual quartz, vuggy : Tucari


J.W. Hedenquist 20

Sonomi volcano

1 km

Nansatsu district, S Kyushu, looking east: Iwato HS deposit, Maruyama pit Inset: qtz-alun halo, sharp ctc with vuggy qtz, to r.)


J.W. Hedenquist 21

Urashima et al., 1981

Tuff breccia Nansatsu Group

Mohong Hill quartz-alunite

lithocap


J.W. Hedenquist 22

Most ore (~70%) in root zone of lithocap, in Lepanto fault

Lepanto fault

Hedenquist et al., 1998; Chang et al., 2011

Cretaceous-Paleogene Lepanto metavolcanics

Late Oligocene to mid-Miocene Apaoan volcaniclastics

12-13 Ma Bagon intrusive complex

Slightly younger Balili volcaniclastics

Qtz diorite porphyry

Chang et al., 2011

1 km


J.W. Hedenquist 23

Pliocene volcanism

3.3 - 1.8 Ma, multiple eruptions

Imbanguila dacite porphyry (3.3-1.8 Ma)

Imbanguila pyroclastics (3.3-1.8 Ma)






Chang et al., 2011

1 km

Young cover: <1.2 Ma

Lapangan Tuff (0.19 Ma)

Imbanguila dacite porphyry (3.3-1.8 Ma)

Imbanguila pyroclastics (3.3-1.8 Ma)






Bato dacite porphyry (1.2 Ma)

Bato pyroclastics (1.2 Ma)

Chang et al., 2011

1 km


J.W. Hedenquist 24

1 km

Chang et al., 2011

NW end of lithocap: qtz-alunite cliffs at unconformity, with kaolinite halo

1 km

X Small workings,

1-4 g/t Au

Breccias

Chang et al., 2011

< 50 ppb Au


J.W. Hedenquist 25

Lepanto HS: 1 Mt Cu & 120 t Au

FSE porphyry: >650 Mt @ 0.65% Cu &

1.2 g/t Au

Guinaoang porphyry, 500 Mt @ 0.4% Cu

& 0.4 g/t Au

Mohong Hill porphyry + HS

Victoria veins, 11 Mt @ 7.3 g/t Au + Ag-

Cu-Pb-Zn

Nayak veins

Teresa veins, 0.8 Mt @ 5.74 g/t Au

Buaki porphyry

Chang et al., 2011

1 km

1.8-2.2 Ma

1.45 Ma


J.W. Hedenquist 26

X-section

Porphyry systems Sillitoe, 2010

Base of lithocap

Residual quartz (vuggy)

Early: High T magmatic   Coupled brine + vapor   Potassic (~500oC) +

advanced argillic lithocap   Wavy qtz veins, no halo   Metal sulfides

Quartz-alunite

Sericitic

Cp, tn

± enargite, Au


J.W. Hedenquist 27

Erosion level?


J.W. Hedenquist 28

after R. Goldfarb, from Groves et al. (2005)

Cu-Au

Intrusion-centered: ~40% of world Au Porphyry: 70% of world Cu


Sillitoe & Hedenquist, 03

Sillitoe and Hedenquist, 2003


J.W. Hedenquist 29

Einaudi et al., 2003

Einaudi et al., 2003


J.W. Hedenquist 30

2 km

2M mica

Hudson (2003)

tonopah, nv: 1901 to late 1920s+, 1.9 moz au, 174 moz ag ... · formation of high- and...

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